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🔋college physics i – introduction review

Mercury Barometer

Written by the Fiveable Content Team • Last updated August 2025
Written by the Fiveable Content Team • Last updated August 2025

Definition

A mercury barometer is a device used to measure atmospheric pressure. It consists of a glass tube filled with mercury that is inverted in a mercury-filled reservoir, with the height of the mercury column indicating the pressure of the surrounding air.

Mercury Barometer cheat sheet for homework

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5 Must Know Facts For Your Next Test

  1. The height of the mercury column in a mercury barometer is directly proportional to the atmospheric pressure, with a higher column indicating a higher pressure.
  2. Mercury barometers are used to measure the absolute pressure of the atmosphere, as the pressure of the mercury column is balanced by the pressure of the surrounding air.
  3. The relationship between the height of the mercury column and the atmospheric pressure is given by the formula: $P = \rho gh$, where $P$ is the pressure, $\rho$ is the density of mercury, $g$ is the acceleration due to gravity, and $h$ is the height of the mercury column.
  4. Mercury barometers are highly accurate and reliable instruments for measuring atmospheric pressure, but they are also fragile and require careful handling.
  5. The use of mercury barometers has declined in recent years due to the development of more portable and digital pressure measurement devices, such as aneroid barometers and electronic pressure sensors.

Review Questions

  • Explain how a mercury barometer is used to measure gauge pressure.
    • A mercury barometer measures the absolute pressure of the atmosphere, which can then be used to calculate the gauge pressure. The height of the mercury column in the barometer corresponds to the absolute pressure of the surrounding air. By subtracting the standard atmospheric pressure (typically 1 atm or 101.325 kPa) from the absolute pressure measured by the barometer, you can determine the gauge pressure, which is the pressure above or below the surrounding atmospheric pressure.
  • Describe the relationship between the height of the mercury column and the absolute pressure measured by a mercury barometer.
    • The height of the mercury column in a mercury barometer is directly proportional to the absolute pressure of the surrounding air. This relationship is given by the formula $P = \rho gh$, where $P$ is the absolute pressure, $\rho$ is the density of mercury, $g$ is the acceleration due to gravity, and $h$ is the height of the mercury column. As the absolute pressure increases, the height of the mercury column will also increase, and vice versa. This allows the mercury barometer to be used as a precise instrument for measuring absolute pressure.
  • Evaluate the advantages and limitations of using a mercury barometer for pressure measurement compared to other pressure measurement devices.
    • Mercury barometers are highly accurate and reliable instruments for measuring atmospheric pressure, as they directly measure the absolute pressure of the surrounding air. However, they also have several limitations. Mercury barometers are fragile and require careful handling, as the mercury is a toxic substance. They are also relatively large and not as portable as more modern pressure measurement devices, such as aneroid barometers and electronic pressure sensors. Additionally, the use of mercury has become increasingly restricted due to environmental concerns, leading to the development of alternative pressure measurement technologies that are more environmentally friendly and easier to use. While mercury barometers remain a valuable tool in certain applications, their use has declined in recent years as newer, more versatile pressure measurement devices have become available.
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